Bag-manufacturing machine

ABSTRACT

A bag-manufacturing machine wherein a tube unwinding from a reel is grasped by a set of rollers, passes into a cutting device with a notched cutter which reduces the resistance of the tube at the points determined by the length of the bags and permits the tube to be entrained, then each bag is successively pulled off by a train of rollers driven at higher speed, its bottom is welded, it is grasped by the mouth, cooled, and transferred onto a collecting drum which, by means of a set of grippers, grasps a certain number of bags which it deposits in a pack on a moving belt for removal.

tates Patent [191 mite Qlass [4 1 Sept. 3, 1974 Mecaniques C. & A., Strasbourg, France [22] Filed: Nov. 22, 1971 [21] Appl. No.: 201,065

[30] Foreign Application Priority Data Nov. 30, 1970 France 70.43599 July 16, 1971 France 71.26954 Oct. 28, 1971 France 71.39448 [56] References Cited UNITED STATES PATENTS 2,333,440 11/1943 Potdevin 93/26 mvmle'lo -3 A 2,680,471 6/1954 Mercer 93/27 2,952,299 9/1960 Finkc 156/498 3,075,678 1/1963 Huck 93/33 R 3,506,523 4/1970 Cook 156/513 Primary ExaminerCharles E. Van Horn Assistant Examiner-Caleb Weston Attorney, Agent, or FirmYoung & Thompson [5 7 ABSTRACT A bag-manufacturing machine wherein a tube unwinding from a reel is grasped by a set of rollers, passes into a cutting device with a notched cutter which reduces the resistance of the tube at the points determined by the length of the bags and permits the tube to be entrained, then each bag is successively pulled off by a train of rollers driven at higher speed, its bottom is welded, it is grasped by the mouth, cooled, and transferred onto a collecting drum which, by means of a set of grippers, grasps a certain number of bags which it deposits in a pack on a moving belt for removal.

10 Claims, 15 Drawing Figures an n e PATENTEDSEPV wn 3.833.446 SHEEI 1 0F 9 PATENTED 74 SHEET 9 HF 1 BAG-MANUFACTURING MACHINE The present invention concerns the manufacture of bags or similar articles of plastic or the like materials.

It is known that the said bags or the like are made from a tube which is delivered in reels of the width of the bag to be obtained and is driven by a device which cuts the tube to the length of the desired bag and closes its bottom by welding by heat, then ejects it for removal, when completed.

As the welding is not instantaneous, especially in the case of a thick plastic material, most machines work intermittently, and therefore cannot have a good output. Moreover in order to obtain continuous unwinding of the reel compensator devices are provided between the said reel and the actual machine, and these elements do not always permit correct'unw'inding of the tube, especially when a large reelis concerned, such as it is advantageous to use in order to avoid excessively frequent reloadings which involve stoppage of the machine. Rotary machines also exist, the output of which is better, but they do not permit the use of thin plastic materials, which however are the most advantageous since a larger number of bags is obtained for an equal weight of material.

Finally the rotary machines which permit the manufacture of bags of thin plastic material have the serious defect of not producing bags with solid bottoms and the mouths of which open easily.

All the currently existing machines have a rate which is limited by the difficulties of ejection and reception of the finished bags. Thus they all have a poor output.

BRIEF SUMMARY OF THE INVENTION In order to remedy these drawbacks, the invention has for its object a machine wherein the tube unwinding from the reel is grasped by a set of rollers, passes into a cutting device with a notched cutter which reduces the resistance of the tube at, the points determined by the length of the bags and permits the tube to be entr'ained,'then each bag is successively pulled off by a train of rollers driven at higher speed, its bottom is welded, it is grasped by the mouth, cooled, and transferred onto a collecting drum which, by means of a set of grippers, grasps a certain number of bags which it deposits in a pack on a moving beltfor removal.

FURTHER DESCRIPTION AND ADVANTAGES OF THE INVENTION drum, an auxiliary drive with tension-regulator device before the drive roller, in providing a suction device in place of the gripper device for the transfer between the sealing drum and the collecting drum, and a device for regulating the position of the welding'drum, in providing the welding grippers with interchangeable ele ments, in the provision of a water-cooling system which is more effective than air cooling, in improving the ejection device, in equippingthe said machine with safety devices in the case of stoppage of function, a special device for the constitution of packets of bags and a device for the regulation of speed and temperature.

In this second version the machine retains all the elements of the first embodiment as described above, with the exception of the packet ejection device, which is replaced by another with higher performance, but their arrangement is different, especially in the obliquity of the path'of the band of material before its arrival on the sealing drum, which can vary between the horizontal and the vertical, the oblique position being preferable since it facilitates movement of the band by gravity, but the positionings of the unwinding reel and the bag ejection system correspond to those of the conventional machines.

The new arrangement necessitates the addition of a first transfer drum placed before the sealing drum, equipped with a suction device effecting the displacement of the previously cut bag. It possesses the considerable advantage of being surrounded by the same straps as those which surround the sealing drum and which have even been extended to the transport rollers, in order better to support and guide the band. This new general arrangement presents the immense advantage of reducing the free space between the drive rollers and the sealing drum, which avoids blockages and thus wasted material and stoppage of the machine, when the material to be transported is heavily charged with static electricity.

The elasticity of the material to be transformed, the wall thickness of which may be less than 2/100 mm. and the modulus of elasticity of which is low, necessitates an auxiliary drive device permitting the feeding of j the machine with a band under constant tension, and

the grippers of the transfer drum of the first-mentioned version of the machine are advantageously replaced by a suction device. j

The angular position of the Welding drum varies according to the length of the bags to be manufactured. To facilitate its positioning in relation to the other elements of the machine, its drive is effected by means of a compensating gearing of unlimited stroke, controlled by a servo-motor.

In all the plastic bag manufacturing machines the welding grippers are covered with a layer of Teflon which has the property of preventing adhesion of the molten plastic material to the metal. This Teflon is subject to wear by reason of the very high speed of the machine according to the invention which instead provides grippers having cheap detachable elements which necessitate only a very short stopping time of the said machine for their replacement.

The variable-speed chain-type ejection device as described in the first version of the machine has been considerably improved by the addition of a new device comprising a retarding drum on the said chain the speed of which is no longer variable but very slow.

When the machine is stopped for any reason, the rear parts of the bags already engaged in the welding grippers are totally molten, which necessitates careful cleaning and a loss of time; this is why one of the improvements in the said machine consists in equipping it with a safety device which causes the bottoms of the bags to disengage themselves from the welding grippers in the case of stoppage.

Another improvement in the machine according to this second form of embodiment permits the automatic regulation of the welding temperature for each running rate, which avoids the tasks of monitoring and verification during the acceleration period of each restart of the machine.

As is self-evident, the machine can advantageously be supplemented by numerous known devices, such as equipment for cutting out grasping handles permitting of manufacturing carrier bags, perforation equipment permitting of obtaining aerated bags, printing elements permitting of obtaining printed bags in a single operation.

According to a further characteristic of the invention the welding members with interchangeable elements can be equipped, by way of'anti-adhesion agent, with glass fibre fabric utilised in such a way that its thermal deterioration is retarded to such extent that its use does not constitute an impediment to the industrial exploitation of a high-speed machine of the rotary type. It is apparent that this considerable advance can be trans- 'ferred to the present-day low-speed machines which work on what is called the alternating principle.

The invention will moreover be clearly understood with the aid of the followingdescription given with reference to the accompanying drawings, which are given only by way of non-limitative example of the invention.

BRIEF DESCRIPTION OF THE VIEWS IN THE DRAWINGS FIG. '1 is an external view of a machine according to the invention, Y, i

FIGS. 2 and 3 represent a sectional view of the same machine, separated along'the line A A, on a different scale, v

FIGS. 4' and 5 represent diagrammatically a variant of embodiment of the machine and the arrangement of its various parts,

FIG. 6 shows the angular. position of the welding drum as a function of the length of the bags,

FIG. 7 represents the welding gripper with its detachable part,

FIG. 8 represents the retarding drum and the dis charge chain,

. FIG. 9 is a section of the retarding drum,

FIG. 10 is a perspective view of a packet of bags,

FIG. 11 represents. the double cutter,

FIG. 12 represents the perforating cutter,

FIG. 13 represents the device for welding the holes,

FIG. 14 is a lateral elevation of a variant of the weld ing device, the movable flap being equipped with glass fibre fabric, and

FIG. 15 is a view analogous with FIG. 14, the device being in the welding position.

DETAILED DESCRIPTION OF THE PREFERRED 1 EMBODIMENTS roller 5. It passes under a cutting device comprising a fixed cutter 6 mounted in a support 7 and a rotating cutter-8. The cutter 6 is smooth whereas the cutter 8 is notched at different points..ln the position as indicated in FIG. 2 the cutters 6 and 8 are in. contact with the tube and effectits transverse cutting except for the positions where the cutter 8 is notched. Thus there is produced an interrupted cut of such nature that the different cut sections, although partially cut, still remain attached to one another. Thetube thus cut is drawn by a further intake device composed of a lower roller 9 and an upper roller 10. It is then entrained by an assem-' bly of ,lower belts 11 and an upper assembly 12 toa train of rollers composed of a lower cylindrical roller 13 and an upper segmented roller 14, which cooperate, according to the selected bag format, either with the lower and upper roller trains 15 and 16, or withthe train 17 and 18, or with the train 19 and 20. The three lower rollers 15, 17, 19 are driven with a periodical vertical movement. The one of them which corresponds to the selected format comes into contact with the upper roller as soon as the roller 13 comes into contact with the segmented roller 14. Whereas the rollers 15, 16, 17, 18, 19 and 20 possess the same linear speed as the rollers 4 and 5, 9 and 10, which is the same as that of the belts 11 and 12. The rollers 13 and 14, which in fact are rolls mounted on'the same spindle but separated bythe belts, have a higher speed equivalent to that of the welding drum'2l. This is the reason why at the moment when the segment of the roller 14 comes into contact with the roller 13, a section of the tube is detached by reason of the speed difference. This separation takes place by tearing off of the parts which were notcut because of the notchings of the cutter 8. This tearing off takes place only when the end of the tube is in the vicinity of the belt roller 22, just a little before the tube is gripped between the roller 22 and the drum 21. So that the section may arrive at this point without damage, it is accompanied in its course by the train of perforated belts 23 rotating at the same linear speed as the drum 2]. The said belts 23 pass beneath the suction box 24, the lower lid of which is perforated and in which a negative pressure is created with the aid of the pump. The tube is thus sucked against the perforated belts and conducted in all safety towards the roller 22. To avoid any deformation and faulty workmanship if the tube is of the bellows-fold type, the train of lower belts 11 has been extended and brought as close as possible to the drum 21, by means of the roller 25. furthermore care has been taken to insert a blower 26, which carries the tube on a cushion of air, into the corner formed by the roller 25, the train of belts 23 and the drum 21.

When the section is gripped between the roller 22 and the drum 21 it continues its course, and is held on the drum 21 over about 270 by the train of belts 27.

' vided with a series of holes connected to an air suction device 30. The rear part of the section which rests on the flap 29 and is sucked by the device 30 is thus turned downwards towards the interior of the drum. Above the drum and at a certain distance from the roller 22, a blowing chest 31 projects air onto the rear part of the section to prevent it from gaping if it is of the bellowsfold type, since the flap 29 draws by suction only upon its lower part. According to one variant of the invention the blowing chest 31 can be replaced by a mechanical device which accompanies the flap 29 and thus the section in the course of their descending movement.

The lowering of the flap 29 is continued until the rear part of the section rests on the fixed welding element 32. At this moment the welding gripper-33 descends so that the rear part of the section is wedged between the parts 32 and 33. The element 32 constitutes the actual welding bar, while the gripper 33 has in its forward part a counter-presser bar 34 which can for example be of silicone rubber. This bar can also be replaced by a heating element to increase the production rate in the case of thick plastic material.

In the course of its rotation with the welding drum 21, the forward part of the section arrives in the vicinity of the transfer drum 35 which carries grippers 36 disposed to be able to enter the grooves 37 of the welding drum 21. When the forward part of the section presents itself at the tangential point of the drums 21 and 35, the grippers 36 are already engaged in the grooves 37. They then close to grasp the end of the section which has become a bag and bring it towards the collecting drum 38. Thus the forward part of the bag has left the welding drum 21 while the rear part is still on it. In order to free it, the welding gripper 33 and the flap 29 rise again and at the same time the air suction in the suction device 30 is halted. As soon as the welding gripper 33 is lifted. the rear part of thebag is completely freed, and the still soft weld can contract, which imparts great firmness to it, and as moreover the transfer drum 35 pulls upon the forward part of the bag the weld is not subjected to any force unfavourable to its strength.

ln thecourse of its subsequent path the transfer drum 35 brings the forward part of the bag to the collecting drum 38. The grippers 36 enter the grooves 39 of the drum 38, open and transfer the bag to the grippers 40 and 41 of the drum 38, which are coaxial but each possesses its own cam and lever device, permitting of controlling their opening and closure separately.

When the first bag is grasped by the grippers 40 and 41, it carries out a complete revolution in the course of which it passes along a blowing mechanism 42 and 43, both parts of which are equipped with a series of nozzles 44 the emitted air of which cools the weld. A series of guides 45 prevents the bag from coming into contact with the nozzles, and the air blown into the interior of the machine is evacuated by the suction nozzles 46.-

When the drum 38, with its first bag held by the grippers 40 and 41, has carried out about three quarters of a revolution, the grippers 40 open while the grippers 41 remain closed and continue to hold the bag. When the gripper assembly comes in front of the transfer drum 35, a second bag has just been brought to the drum 38. The forward part of the bag comes to rest on the backs of the grippers 41 and will be grasped by the grippers 40. In the course of the revolution of the drum 38 the grippers 41 will open and reclose, while the grippers 40 will remain closed. Therefore the two bags are now grasped by the grippers 40 and 41. The same procedure is followed until the desired number of bags collected by each set of grippers has been obtained, which number will vary as a function of the thickness of the tube .on a pair of chains 48 which are held on four pairs of wheels 49. The left ascending part of the chains passes in the vicinity of the drum 38. When the grippers 40 and 41 are in the proximity of this part, the grippers 47 are also situated there. At the moment when the grippers 47 close to grasp the bags, the grippers 40 and 41 open and release them. The grippers 47 draw the bags to the right, passing over a protective gutter 50 onto an endless belt 51 and when the whole length of the bags is resting on the belt the grippers 47 open and release the packet against a stop 52 which is regulable according to the format. 1

As plastic materialshave a tendency to stick to the rotating parts when they are charged with static electricity, apertures 53 are provided in the drum 38 to permit a fixed blower 54 to detach the bag closest to the drum at the moment when the grippers 47 grasp the bags to carry them on to the endless belt 51, to which a mechanism imparts a lateral advancing movement so that the different packets overlap like the slates of a roof.

At the moment when the grippers 47 grasp the bags to remove them from the drum, the chain 48 must have the samelinear speed as the drum; now this speed is high and it is not conceivable to obtain a suitable reception of the bags if the speed of the chain is not retarded. This is why a mechanical drive by elliptical pinions has been provided which permits of periodically varying the speed of the chain, the maximum value of which will be at the removal of the packets of bags and the minimum will be at their depositing, which thus will be effected gently, without deformation of the packets.

To facilitate the work of the machine operator and the cleaning of the machine and to guard against any incidents in operation, various devices have been provided which render all parts of the machine accessible. Thus the belts 27 are mounted in a frame 55 which pivots about a spindle 56 by means of a jack 57. Likewise the belts 23 and 12 are mounted in a frame 58 which opens at front or rear by means of a jack (not shown). The hood of the blower 42 can pivot about a spindle 59 by means of a pneumatic jack 60 in order to clear the collecting drum, and the hood of the upper blower 43 slides horizontally to the position 43' marked in dotted lines, clearing the upper part of the drum.

As is self-evidentand as appears moreover from the above, the invention is in no wise limited to that of its manners of application nor to those of the forms of embodiment of its various parts which have been more especially indicated. On the contrary it includes all variants thereof, such as that where the machine does not manufacture bags but analogous articles. Another variant is where pneumatic guide systems replace mechanical guide systems or vice versa, and where mechanical devices are replaced by others, notably where the grippers, with which the drums 35and 38 and the chains 48 are equipped for the collection and ejection transferences, are replaced by pricker devices which in fact are needles aligned on bars which can enter the drum and issue therefrom. The transfer operation is then much simpler and the equipping of the machine is less onerous. For the transference of the bag the points enter its forward part and hook to it. When the transfer drum 35 gives the bag to the collecting drum 38, the points of the drum 35 are retracted while those of the drum 38 are extended, the collecting of the plurality of bags one upon the other being effected in a simpler manner than with the grippers. Likewise, when the drum 38 leaves the bags to pass them to the discharge chain, the points of the drum 38 retract while those fixed in place of the grippers 47 of the chain 48 are extended. Finally to deposit the bags on the discharge belt the points of the chain 48 retract, dropping the packet of bags. I

This varient is utilised with advantage every time the presentation of the bag and its sealingare' notimportant, since the priekersleave small holes in the mouth of the bag. In the contrary case the device with grippers is preferable.

According to a second form of embodiment of the invention, which is represented diagrammatically by FIGS. 4 and 5, a reel 1 of tubular or sheet plastic material rests with its spindle 2 on a support of known form.

The plastic material passes over a deflecting roller 3, then into an auxiliary drive device composed of the rollers 61 and 62, the roller 61 being driven by a variablespeed motor. The band then passes over the rollers 63 and 64. The rollers 63 are mounted on a rocking arm 65 which can oscillate about its axis. According to the band tension prevailing between the auxiliary drive device and the main drive .device composed of the rollers 4 and 5, the rocking arm assumes a different position which, by means of an electric detection device known per se, modifies the speed of the motor of the auxiliary drive 61 62 and thus permits feeding of the machine with band under constant tension] When the machine is supplied with tubular material, this passes directly from the last roller 64 to the main drive device 4 and asindicated by the solid line in FIG. 4.

When it is supplied by a band of open material, this is directed towards a known tube-formation and lengthcutting station S, represented in dot-and-dash lines in FIG. 4, before arriving at the drive device 4 5, from which it' is entrained as-indicated for the first form of embodiment of the machine. However the pathis advantageously oblique, which has the advantage of shortening the machine and makinguse of the weight of the material itself, which facilitates the material travel. This obliquity commences at the horizontal and terminates at the vertical, which themselves are utilisable in accordance with the invention.

This oblique arrangement no longer permits direct feed of the sealing drum 21. Thus a first transfer drum 66 is provided the outer shell of which is pierced with a series of holes 67 which are connected to a suction pump through a chamber 68, a pipe 69 and a hollow shaft 70, a rotary distributor placed between the latter and the compressor permitting of supplying the chamber 68 at will. When the transfer drum 66 is in the position as indicated in FIG. 4, the suction takes place upon the forward part of the bag and entrains the latter towards the sealing drum 21. At the moment when the beginning of the bag commences to be inserted between the belts ll and the drum 21, the rotary distributor cuts off the compressor from the chamber 68,

can be" engaged freely between the belts 11 and the drum '21.

This new arrangement possesses a considerable advantage over the old one, by reason of the fact that the endless belts 11 guide the bag throughout its path without interruption, from its cutting off.

The second transfer drum 35, which comprises the grippers 36 in the first form of embodiment of the machine, is advantageously. replaced by another of the same dimensions, but inwhich thetransference is effected no longer by grippers but by suction as in the drum 66. I

Above the drum 35' there is a rotary element 71 which carries at its end a bar 72 capable of retaining a small quantityof water or refrigerant liquid contained in a basin 74 and distributed by a roller device,75. The angular positionv of the arm 71 is regulated so that it comes into contact with the weld which has just been effected. So that slight variations of the position of the bag .due to theelasticity of the-materialv may be compensated, the bar 72 is wider than the weld, and moreover the arm 71 is controlled by means of a positioning differential which permits of precise adjustment of its position during operation.

The bag is brought to the drum 38 on which the packets are collected which are then taken up again by the ejector drum 76, the role of which is considerably to retard the packet of bags coming from the drum 38. Chains 48 turning at low speed can then easilytake the packet and deposit it on the belt 51 which moves, according to a preferred embodiment of the invention, transversely of the machine.

As this machine is of variable format, it can manufacture bags of various formats and thus must be equipped with a certain number of devices permitting of obtaining the corresponding adjustments.

One of the principal characteristics of this machine resides in the fact that its adjustments are greatly simplified in comparison with other machines known at present. One of the particular points of the invention concerns the regulation of the position of the welding drum 2]. As the weld is effected from the rear of the bag, the only adjustment when the length of the bag is changed consists in changing the angular position of the drum 21 in relation to the drums 66, 35, 38 and 76, for which the initial adjustment is valid irrespective of the length of the 'bag. To this end a differential of unlimited stroke has been inserted into the kinematic chain of the machine. This differential, controlled by a motor and push button, permits of varyingthe angular position of the drum 21 in relation to the others. In FIG. 6 it is seen that tube lengths 77 are brought continuously by the first transfer drum 66 onto the drum 21 and beneath the belts 11 (not shown). Three bags are engaged on the drum 21 and their rear parts rest on the flaps 29. The second transfer drum 35 has the task of discharging the welded bags by grasping them by their mouths. When the bag length changes, it is'sufficient to reposition the drum 21 in relation to the other drums which retain their initial positions. In fact, if the bag becomes shorter it'is sufficient to shift the drum 21 so that the flaps 29 come into the new position as represented in dotted lines. As the front of the bag always remains in the same position as previously, the positions of the drums 66 and 35 also remain the same.

As already explained, the welding gripper must be capable of being replaced rapidly, and the detachable part must be of low cost. To this end, according to a preferred form of embodiment of the invention. as represented in FIG. 7, the welding drum comprises twopart blocks 78 and 79 each of which has a cavity, into which the electric heating resistance 80 is inserted, and it is the piece 82 which effects the weld and is covered with a protective coating of Teflon. This piece is held between the pieces 78 and 79 by gripping by the screws 81. This arrangement ensures an excellent heat transmission between the parts 78, 79 on theone hand and the part 82 on the other. To change'the piece 82 it is merely necessary slightly to slacken the screws 81, then withdraw and replace the piece. Thus there is only a minimum of work and time lossin the case of a breakdown. lt is quite apparent that other forms may be given to the piece 82, such for example as that of an inverted T which would slide into a corresponding groove in the gripper body. i

At the very high operating rates which are characteristic of the machine according to the invention it is impossible to eject the bags or packets of bags directly, since they have acquired too much kinetic energy in relation to the very low rigidity of thematerial of which they are made. This is the case particularly with bags of plastic material of the category of the polyolefines. This is why the machine has been equipped with'a retarding device which permits of effecting the ejection and reception of the bags at low speed, thus under very good conditions. This device is illustrated in-FIGS. 8 and 9, where one may see the collecting drum 38 equipped with grippers or prickers, which brings the packets of bags to the region which corresponds substantially to the tangential point with the retarding cylinder 76, which is composed of two discs. At this precise moment a series of grippers 83 articulated in two arms 84 by means of the levers 85 and rollers 86 which circulate on two cams (not shown) move down towards the block 87 and strongly grip the packet of bags. The passage of the bags from thedrum 38 to the arms 84 is effected at high linear speed, since the grippers 83 and the block 87 move at the same peripheral speed as the drum 38 which is equipped with grooves 39 so that the grippers 83 may open there to grasp the bags and reclose freely, which operation is represented in dotted lines in FIG. 8. When the arm 84, in the course of its rotation, arrives in the position represented in solid lines, three movements occur simultaneously: the grippers 83 open to free the fronts of the bags, the grippers 47 of the chain 48 commence to reclose and the retarding device comes into action again. It comprises two discs 76 which rotate in the same direction as the arms 84, but which are driven with a very slow rotating movement which is obtained through the intermediary of a pinion 88 mounted on its spindle 89 and meshing with a toothed wheel 90 fast with the discs 76. This assembly can rotate freely on the shaft 91 through the intermediary of the ball bearings 92, and the shaft 91 rotates more rapidly as it carries the arms 84 which are keyed on it. Around this rotating assembly there is a series of hoops 93 of any desired section. These parts are fixed and gripped in the parts 94, which are themselves fast with the main frame of the machine through the in-- termediary of the shafts 95.

The retarding device likewise comprises a roller 96 mounted on a shaft 97. The linear speed of the roller 96 corresponds to the linear speed of the discs 76. The shaft 97 is mounted in a pair of levers 98 which can oscillate about the centre 99, and each of them carries at its end a roller 100 which rests on a cam 101. The application of the roller 100 is effected by means of the spring 102 which bears on afix'ed part 103. At the moment when the retardation of the packet must be effected, the cam 101 is in a position such that the roller 96 is applied to the discs 76. As the gripping is effected on the rear part of the bags, the effects of the kinetic energy contained in the packet of bags are eliminated. Moreover the fixed hoops 93 on which almost the whole load of the bags rests give rise to a very useful supplementary braking action. As soon as the retarding of the bags is effected, the grippers 47 close upon the said bags, which are entrained at slow speed towards the reception belt.

So that the retardation may'be effected under optimum conditions, it is necessary that the gripping of the bags between the rollers 96 and the discs 76 should be effected on their rear parts. As the machine is variable as to format, it will also be necessary that the position of the roller 96 and its control device should also be variable, and that the position of the assembly may pivot about the shaft 91. Thus it will be mounted on a distinct frame capable of pivoting about this axis.

The device for collection on the drum 38 and the 'retarding device as described above are usable as such not only on the two forms of embodiment as described but also upon known slower machines where the ejection system is not provided to form packets of bags.

The machine according to the invention is equipped with a safety device so that in the case of a stoppage the bags engagedbetween the drum 21 and the belts 11 may not be melted. In the first form of embodiment it was seen that the rear parts of the bags are fixed by suction on flaps 29 which in normal running are connected to a pump through the intermediary of a distributor and that the bag rear parts are turned downwards towards the welding grippers. So as to be able to avoid engagement of the bag between the welding grippers in the case of stoppage of the machine, the pipes 30 are connected by means of another distributor to the blowing part of the pump, which has the effect of projecting the rear parts of the bags towards the belts 11 and prevents them from being engaged between the welding gripp FIG. 10 shows how a packet of interconnected bags appears. At their rear part there is the weld 104, at their front part the perforation 105. The different bags have been interconnected byfusion over the whole perimeter of the holes 106. The packet is hooked by the holes 106 on to a board having two nails. A pull upon each bag detaches it along the perforation 105.

The means of manufacturing packets having two circular holes 106 in their upper part will be indicated in the following description and in FIG. 10. It is understood that a packet can be constituted according to the same principle of fusion of the bags withone another, but utilising one or more holes of any desired section. According to a preferred manner of realisation of the invention these holes will be circular, as this facilitates the mechanical realization,

To manufacture such packets, the machine is equipped with two small supplementary devices, one serving to make the line of perforation 105, the other serving to make the holes 106 and to effect the fusion of the bags to one another along the circumference of these holes. The cuttingof the material 107 iseffected by means of the lower cutter 6 and the upper rotating cutter 8. To obtain the perforation line 105 it was necessary to complete the cutting device with a second cutter 108, FIG. 12, the distance of the edge of which from that of the cutter 8 corresponds to that of the lines 107 and 105. To obtain the perforation the cutter, 108 has a large number of notches 109. After this operation the bags are taken by-the machine to ejection in known manner; I

To'make the holes and to weld their contours together the chain 48 as represented in FIG. 13 is equipped in a special way. The block 110 which carries the grippers 47 comprises two cylindrical pieces which can slide in guides 112 under the action of a ramp 113 and a return spring 114. The parts 111 are partly hollow and comprise anelectric resistance in this region, which permits their heating. Their electric current supply is effected by means of sliding contacts of known type. The packet of bags grasped and drawn by the grippers 47 and the block 110 advances slowly from right to left. The head of the partlll slides along the ramp 113 and drives gently into the forward part of the bags under the pressure of the'said ramp, piercing them by-fusion. When the assembly arrives at the end part of the ramp, the part 111 withdraws leaving a hole, a fused circumference of which has permitted of welding the bags to one another."

The machine according to the invention is equipped with an automatic vdevice .which permits of effecting temperature and speed regulations without any manual intervention, which is especially useful in the acceleration phase at each starting-up. For every material thickness one knows the necessary temperature of the welding grippers for a given production rate, just as one knows the maximum production rate which it is reasonable to expect I The instrument panel of the machine comprises a dial on which the anticipated production rate can be shown, a dial on which the welding temperature at slow speed of the machine can be indicated and a dial on which the welding temperature necessary for the anticipated production rate can lie-indicated. v

It is known that the welding temperatures are substantially proportional to the speed of the machine.- On many machines with low production speeds the fusion temperature is corrected automatically as a function of the speed. This method has proved inadequate for a fast machine, since if the acceleration is great it is possible for the machine rapidly to achieve an operating rate such that, despite the temperature correction devices, the grippers have not had time to heat up sufficiently. The automatic control device according to the invention is in fact a brain which permanently monitors the concordance between the temperature and. the speed, so that the machine cannot accelerate if the temperature is not yet reached; although one may not know the temperature necessary for an intermediate speed, it is sufficient to know the slow speed temperature and the maximum speed temperature.

This device will dispense with consideration of the three buttons described above, when they have been adjusted, and with pressing an automatic'acceleration button, as the machine itself permanently seeks the permitted speed for the temperature which the grippers have just reached- If for any reason the operator does not wish to accelerate to the speed pre-determined on the dial, another button permits of interrupting, at any moment, the acceleration of the machine which will continue to operate at the speed which it has just reached.

As described above, the welding device-comprises a movable flap 29, a welding element 32, a welding gripper 33 with a counter-presser bar, 34 which comprises a bar of silicone rubber in order to avoid adhesion with the material to be welded.

A further characteristic of the invention consists in fixing a piece of glass fibre fabric on the movable flap 29, so that there is an overhang upon which the rear part of the bag 116 is placed, upon which the weld is to be effected in 1 the course of the rotation of the drum 21.

FIG. 15 shows the welding position: the flap 29 has descendedin the course of the rotation, and with it the fabric 115, and by virtue of the holes in the latterwhich coincide with those of the flap 29'which are connected to the suction system 30 (not shown), the rear part of the bag 116 also descends, but can no longer come into contact with the element 32 directly, since it is insulated by-virtue of the glass fibre fabric 115.

The welding gripper 33 with its bar 34 is likewise shown in the closed position.

It is recalled, by way of reminder, that the bar 34 can for example be constituted by silicone rubber or ordinary heat-resistant rubber wrapped in glass fibre fabric, in accordance with currently known methods.

The glass fibre fabric 115, which in currently existing machines permanently surrounds the. heated element .32, is thus subjected to the same movements as the flap 29, so that at regular intervals it is raised, then lowered towards the element 32 and vice versa. This movement leads to a regular ventilation of the part 115, the lifeof which is thus considerably increased, since in the course of these movements the stored heat is largely dissipated.

It should be noted that the same fibre-glass-lined flap device can be utilised with advantage in other types of machines, especially in bag welding machines with alternating motion in which the welding element and the movable gripper are not rotary.

The fastening of the piece 115 on the flap 29 can be realised in different manners: it is possible to use selfadhesive glass fibre fabric, it is possible to use ordinary glass fibre fabric and to fasten it with self-adhesive strips, or the glass fibre fabric can be fastened by mechanical means, in the present case by bars and screws, either on the upper part, or on the lateral face, or on the rear face 117 of the flap 29.

Furthermore it is possible to insert the glass fibre fabric into a thin metallic frame which is also fixed on the flap 29.

It is quite apparent that a large number of other styles of'fastening exists.

The glass fibre fabric which is used for preference could of course be replaced by insulating foils having identical or analogous properties, without thereby departing from the scope of the invention.

What is claimed is:

1. In a machine for the manufacture of bags of thermoplastic material, comprising means to advance a continuous tube of thermoplastic material, means for severing from said tube relatively short lengths of said materiaL'a welding drum having means thereon for heat sealing closed one end of said relatively short lengths of material, a collecting drum for collecting thereon stacks of said relatively short lengths of material with one end sealed closed, and means for transferring said severed lengths with one end sealed closed from said welding drum to said collecting drum; the improvement in which said collecting drum has pairs of grippers theron for gripping the forward ends of the bags of said stacks, and means to operate said grippers alternately whereby one gripper of the pair grips the severed lengths already in the stack while the other gripper retracts to permit a newsevered length to be added to the top of the stack, after which said other gripper grips the stack and said one gripper retracts to permit a still further severed length to be added to the top of the stack.

2. A machine as claimed in claim 1, and means mounting said grippers of each said pair for swinging movement about a common axis parallel to the axis of said collecting drum.

3. In a machine for the manufacture of bags from thermoplastic material, comprising means for advancing a continuous tube of thermoplastic materiaLmeans for severing relatively short lengths from said tube, a welding drum on which one end of each said relatively short length is heat sealed closed, and a collecting drum on which said relatively short lengths with one end sealed closed are collected in groups; the improvement comprising a transfer drum disposed between said welding drum and said collecting drum and having means thereon for receiving said relatively short lengths with one end sealed closed from said welding drum and transferring them to said collecting drum, said welding drum having means thereon for welding closed the rear ends of said severed lengths, said welding means comprising heat sealing means disposed within the periphery of said welding drum, and means to deflect the rear ends of said severed lengths radially inwardly of said welding drum for engagement with said heat sealing means.

4. A machine as claimed in claim 3, and endless belts encompassing a major portion of the periphery of said welding drum and spaced apart in a direction parallel to the axis of the welding drum, said heat sealing means being disposed entirely within the contour of said belts.

5. A machine as claimed in claim 3, said deflecting means comprising a flap mounted for swinging movement about an axis parallel to the axis of the welding drum for movement between an outer position in which the outer surface of the flap lies on the periphery of the drum, and a radially inner position in which the flap directs said rear ends of said severed lengths toward said heat sealing means.

6. A machine as claimed in claim 5, said flap having a glass fiber surface that contacts said material, said glass fiber overhanging said flap to occupy a position in said inner position of said flap between said material and a lower portion of said heat sealing means thereby to prevent adhesion between said lower portion of said heat sealing means and said material.

7. A machine as claimed in claim 5, and means urging said material against said flap as said flap moves radially inwardly.

8. A machine as claimed in claim 7, said urging means comprising means directing air radially inwardly against said rear ends of said flap.

9. In a machine forthe manufacture of bags from thermoplastic material, comprising means for advancing a continuous tube of thermoplastic material, means for severing relatively short lengths from said tube, a welding drum on which one end of each said relatively short length is heat sealed closed, and a collecting drum on which said relatively short lengths with one end sealed closed are collected in groups; the improvement comprising a transfer drum disposed between said welding drum and said collecting drum and having means thereon for receiving said relatively short lengths with one end sealed closed from said welding drum and transferring them to said collecting drum, said groups comprising stacks, said collecting drum having thereon pairs of grippers for gripping the forward ends of the bags of said stacks, and means to operate said grippers alternately whereby one gripper of the pair grips the severed lengths already in the stack while the other gripper retracts to permit a new severed length to be added to the top of the stack, after which said other gripper grips the stack and said one gripper retracts to permit a still further severed length to be added to the top of the stack.

10. A machine as claimed in claim 9, and means mounting said grippers of each said pair for swinging movement about a common axis parallel to the axis of said collecting drum. 

1. In a machine for the manufacture of bags of thermoplastic material, comprising means to advance a continuous tube of thermoplastic material, means for severing from said tube relatively short lengths of said material, a welding drum having means thereon for heat sealing closed one end of said relatively short lengths of material, a collecting drum for collecting thereon stacks of said relatively short lengths of material with one end sealed closed, and means for transferring said severed lengths with one end sealed closed from said welding drum to said collecting drum; the improvement in which said collecting drum has pairs of grippers theron for gripping the forward ends of the bags of said stacks, and means to operate said grippers alternately whereby one gripper of the pair grips the severed lengths already in the stack while the other gripper retracts to permit a new severed length to be added to the top of the stack, after which said other gripper grips the stack and said one gripper retracts to permit a still further severed length to be added to the top of the stack.
 2. A machine as claimed in claim 1, and means mounting said grippers of each said pair for swinging movement about a common axis parallel to the axis of said collecting drum.
 3. In a machine for the manufacture of bags from thermoplastic material, comprising means for advancing a continuous tube of thermoplastic material, means for severing relatively short lengths from said tube, a welding drum on which one end of each said relatively short length is heat sealed closed, and a collecting drum on which said relatively short lengths with one end sealed closed are collected in groups; the improvement comprising a transfer drum disposed between said welding drum and said collecting drum and having means thereon for receiving said relatively short lengths with one end sealed closed from said welding drum and transferring them to said collecting drum, said welding drum having means thereon for welding closed the rear ends of said severed lengths, said welding means comprising heat sealing means disposed withIn the periphery of said welding drum, and means to deflect the rear ends of said severed lengths radially inwardly of said welding drum for engagement with said heat sealing means.
 4. A machine as claimed in claim 3, and endless belts encompassing a major portion of the periphery of said welding drum and spaced apart in a direction parallel to the axis of the welding drum, said heat sealing means being disposed entirely within the contour of said belts.
 5. A machine as claimed in claim 3, said deflecting means comprising a flap mounted for swinging movement about an axis parallel to the axis of the welding drum for movement between an outer position in which the outer surface of the flap lies on the periphery of the drum, and a radially inner position in which the flap directs said rear ends of said severed lengths toward said heat sealing means.
 6. A machine as claimed in claim 5, said flap having a glass fiber surface that contacts said material, said glass fiber overhanging said flap to occupy a position in said inner position of said flap between said material and a lower portion of said heat sealing means thereby to prevent adhesion between said lower portion of said heat sealing means and said material.
 7. A machine as claimed in claim 5, and means urging said material against said flap as said flap moves radially inwardly.
 8. A machine as claimed in claim 7, said urging means comprising means directing air radially inwardly against said rear ends of said flap.
 9. In a machine for the manufacture of bags from thermoplastic material, comprising means for advancing a continuous tube of thermoplastic material, means for severing relatively short lengths from said tube, a welding drum on which one end of each said relatively short length is heat sealed closed, and a collecting drum on which said relatively short lengths with one end sealed closed are collected in groups; the improvement comprising a transfer drum disposed between said welding drum and said collecting drum and having means thereon for receiving said relatively short lengths with one end sealed closed from said welding drum and transferring them to said collecting drum, said groups comprising stacks, said collecting drum having thereon pairs of grippers for gripping the forward ends of the bags of said stacks, and means to operate said grippers alternately whereby one gripper of the pair grips the severed lengths already in the stack while the other gripper retracts to permit a new severed length to be added to the top of the stack, after which said other gripper grips the stack and said one gripper retracts to permit a still further severed length to be added to the top of the stack.
 10. A machine as claimed in claim 9, and means mounting said grippers of each said pair for swinging movement about a common axis parallel to the axis of said collecting drum. 